Yes I had one made to fit inside a jockey pod. It was fabricated out of Aluminium with enough space left so that I could line the pod with foam and then I used on of these
on top to fill it with fuel and to take a hose to the engine. so to access the filler you liften the Joackey cushion I then had a fuel tube coiled in the jockey with a quick connect fitting on the end and another quick connect fitting on the fuel filter mounted on the transom so that I could change between the main tank and the jockey tank.
I had to get some special neoprene captive nuts to hold the above fuel adaptor plate onto the top of the tank whilst sealing the holes similar to these once here
All in all it worked really well and held about 35 litres. It was fitted into a leeway single jockey pod which was then screwed down to the deck.